西昆仑阿卡阿孜山岩体的年代、源区和构造意义

阿卡阿孜山岩体是西昆仑造山带中面积最大的花岗岩侵入体，主要由花岗闪长岩和二长花岗岩组成。对其中花岗闪长岩的黑云母^40Ar/^39Ar定年获得了精确的213Ma的表面年龄。这一结果与较早前根据单颗粒锆石U-Pb法获得的年龄结果在误差范围内一致，表明阿卡阿孜山岩体并非是一个多期次的复式岩基，而是同一次岩浆活动的产物。地球化学研究表明阿卡阿孜山岩体为次铝质－轻微过铝质的钙碱性－高钾钙碱性岩体，尽管花岗闪长岩和二长花岗岩之间存在化学组分上的差异，二均具有轻稀土富集的稀土分布模式和相似的微量元素特征。然而二的初始Sr同位素组成存在一定的差异，表明二长花岗岩并非是花册 长岩分异作用的产物。二的Sr-O的同位素共同构成了负相关，排除了在其形成过程中幔源岩浆介入的可能性，反映其源区为包含长英质组分和基性－超基性组分的增生楔物质。由于增生楔的部分熔融需要较高的能量输入，因而阿卡阿孜山岩体不大可能形成于与消减作用有关的大陆边缘环境。此次的黑云母^40Ar/^39Ar年龄十分接近早前的锆石U－Pb年龄，表明该岩体的冷却速率相当快，应反映一种碰撞后抬升的环境。这种环境的出现表明西昆仑古特提斯洋在晚三叠纪时已经闭合。     

粤西阳春中生代钾玄质侵入岩及其构造意义：

粤西阳春地区马山二长闪长岩强烈富集K、Sr和LREE，(87Sr／86Sr)；≈0.7046，εNd(t)≈+1；岗尾-轮水岩体较富集K、Rb、Th和LREE，(87Sr／86Sr)：≈0.7063，εNd(t)≈-2；石岩体较富集Sr，K、Rb、Th和LREE相对较低，(87Sr／86Sr);=0.7084～0.7089，εNd(t)≈-6。马山岩体来源于大离子亲石元素(ULE)和LREE富集的交代地幔；岗尾-轮水岩体来自于放射成因Sr、Nd同位素组成略高或交代时间略早的富集交代地幔，并且经历了明显的结晶分异作用；石岩体则很可能是前存下地壳底垫基性岩重熔形成的。从早侏罗世到早白垩世，南岭西部的岩浆成分和源区的规律性变化反映了区域软流圈地幔上涌和岩石圈伸展-拉张-减薄的演化过程。     

西藏冈底斯带始新世曲水岩基的岩浆混合作用:来自斜长石阴极发光特征和成分变化的证据

斜长石作为主要造岩矿物,是研究岩石成因、示踪岩浆演化和岩浆混合过程的有效工具.对冈底斯带曲水岩基始新世花岗闪长岩、二长花岗岩、闪长岩脉和暗色包体中的斜长石进行了阴极发光图像结构特征、电子探针主量元素和LA-ICP-MS微量元素成分的分析,揭示了斜长石复杂环带的成因和相关的岩浆过程.该区斜长石的阴极发光图像呈现出多种颜色且与其An值相对应,随着An值降低依次为绿色、蓝色和暗灰色或暗红色等,并发育补丁状环带、筛状环带、韵律环带等.花岗闪长岩、二长花岗岩中斜长石的An值具有相似的变化范围(20~55),而闪长岩脉和暗色包体中An值的变化范围较大(25~85),表明曲水岩基经历了复杂的开放过程.微量元素结果表明:花岗闪长岩与闪长岩脉和暗色微粒包体具有相同的Sr含量范围(600×10^-6~1 100×10^-6);而二长花岗岩的Sr含量(1 000×10^-6~2 400×10^-6)整体高于前者.以上研究表明,花岗闪长岩中阴极发光呈现绿色的核部或幔部是偏中性岩浆注入寄主岩岩浆混合的结果;具有高Sr含量的二长花岗岩认为是高Sr含量的岩浆结晶形成的;闪长岩脉和暗色微粒包体中的筛状结构斜长石为寄主岩捕掳晶.     

Origin of Sierra Nevadan granite: evidence from small scale composite dikes

Composite dikes at Hell Hole Meadow, in the central Sierra Nevada, contain hybrids created by small scale mixing of andesitic and rhyolitic magmas. Early rhyolitic injections had partially solidified when subsequent andesitic magmas arrived and mixed with small increments of remnant rhyolitic magma. In major element chemistry, the hybrid rocks define linear MgO-variation diagrams that closely resemble those for the Half Dome, Mt. Givens, and Eagle Peak granodiorites. The patterns suggest that mixing of mafic and felsic magmas has been important in the evolution of these plutons.Hornblendes in three Hell Hole Meadow hybrid rocks ranging from dacite to andesite display indistinguishable crystal-chemical variation patterns. The crystals apparently developed as phenocrysts of endmember andesitic magma prior to the mixing event and retained their compositional character in the hybridization event. Plutonic hornblendes (Dodge et al. 1968; Noyes et al. 1983) display crystal-chemical patterns nearly identical to those in the dike cores making it unlikely that the plutonic hornblendes represent restite of a complex lower crust.Hornblende chemical data from a suite of rocks collected across the width of the compositionally zoned Half Dome granodiorite (Yosemite National Park) define clusters, like their Hell Hole Meadow counterparts, that are very similar to one another despite the large range in host rock bulk composition. Sr isotopic data (Kistler et al. 1986) and linear MgO-variation patterns for the major elements (Reid et al. 1983) suggest that the Half Dome is a mixture of high-alumina basalt and rhyolitic magmas. We propose that while the bulk chemistry of hybrid granodiorites is determined by the proportions of the constituent mafic and felsic magmas, the hornblendes in the mixed rocks largely retain compositions created in the mafic component prior to mixing. Mixing may occur either by incremental addition of felsic magma into a relatively large volume of mafic magma (as at Hell Hole Meadow), or by the chilling and subsequent disaggregation of mafic pillows in a largely felsic host.     

Geochemistry of the Eocene Felsic Porphyric Rocks and High-Mg Potassic Rocks along JARSZ: Implication for the Tectonic Evolution in Eastern Tibet

<正>Eocene felsic porphyric rocks and the high-Mg potassic volcanic rocks(HMPR) occur along the Jinshajiang-Ailao Shan-Red River shear zone(JARSZ) in eastern Tibet.Compared with the HMPR,which are generally believed to be sourced from an enriched mantle,the felsic porphyric rocks show similar K_2O contents,enrichment in LREE and LILE,particularly radiogenic isotope(e.g.Sr and Nd) features much similar to the former,implying generation of the felsic porphyric rocks most likely related to the HMPR,although they both have clearly different major and trace element compositions. The close relationship in spatial-temporal distribution and similar Sr-Nd characteristics between the felsic porphyric rocks and HMPR in eastern Tibet indicate that both of them were possibly formed by a similar tectonic process(event).Combining the basic dikes in southern and eastern Tibet,we suggest that the break-off of north-dipping Neo-Tethyan slab in southern Tibet during 50-40 Ma,triggered formation of high-Mg potassic magma.This led to developing felsic porphyric magma production by partial melting of underplating HMPR in the lower crust,or fractionation crystallization of the high-Mg potassic magmas.The break-off of slab in the Eocene may also have contributed to the abundant ore-forming material related to earlier subduction events,resulting in formation of the porphyric deposits along JARSZ in eastern Tibet.     

Geochemistry of mafic microgranular enclaves in the Tamdere Quartz Monzonite, south of Dereli/Giresun, Eastern Pontides, Turkey

Rocks of the Late Cretaceous Tamdere Quartz Monzonite, constituting a part of the Eastern Pontide plutonism, include mafic microgranular enclaves (MMEs) ranging from spheroidal to ellipsoidal in shape, and from a few centimeters to decimeters in size. The MMEs are composed of diorite, monzodiorite and quartz diorite, whereas the felsic host rocks comprise mainly quartz monzonite, granodiorite and rarely monzogranite on the basis of both mineralogical and chemical compositions. The common texture of felsic host rocks is equigranular. MMEs are characterized by a microgranular texture and also reveal some special types of microscopic textures, e.g. antirapakivi, poikilitic K-feldspar, small lath-shaped plagioclase in large plagioclase, blade-shaped biotite, acicular apatite, spike zones in plagioclase and spongy-cellular plagioclase textures.

The distribution of major, trace and RE elements apparently reflect exchange between the MMEs and the felsic host rocks mainly due to thermal, mechanical and chemical interactions between coeval felsic host magma and mafic magma. The most evident major element transfer from felsic host magma to mafic magma blob is that of alkalis such as Na and K. LILEs such as Rb, Sr, Ba and some HFSEs such as Nb, Y, Zr and Th have been migrated from felsic host magma to MMEs. Apart from these major and trace elements, the other element transfer from felsic host magma to mafic one concerns REE contents. Such a transfer of REEs has evidently increased the LREE contents of MMEs. Enrichments in alkalis, LILEs, HFSEs and REEs could have been achieved by diffusional processes during the solidification of magma sources. The felsic and mafic magma sources behave as Newtonian and visco-plastic materials. In such an interaction, small MMEs behave as a closed system due to immediate rapid cooling, whereas the bigger MMEs suffer greater diffusion from the Newtonian felsic host magma due to slow cooling.     

In situ differentiation and evolution of potassic syenites from Svidnya, Bulgaria

Potassic syenites from Svidnya, Bulgaria crop out as small isolated bodies as the primary for this intrusion liquid has basic to intermediate composition. The evolution in a closed magma chamber created plutonic rocks ranging from basic (melasyenite) to acid (granite) and from metaluminous to peralkaline. The most mafic varieties show cumulative textures typical for orthocumulates with cumulus phases clinopyroxene, biotite, apatite and potassium feldspar as gravitational settling is a viable process for separation of particles in the bottom parts of magma chamber. In the middle stratigraphic level of biggest body modal igneous layering with development of dark (clinopyroxene?+?amphibole) and light (potassium feldspar) laminas was observed. Oscillatory crystallization around eutectic point resulted in cyclic separation of mafic and felsic phases in repetitive layers. Fractionation of Ca- and Al-rich phases—clinopyroxene, biotie and potassium feldspar created peralkaline residual liquid strongly enriched in HFS elements.     

太行山北段石湖金矿的成岩成矿机制:U-Pb年龄及地球化学证据

为讨论石湖金矿的形成与麻棚花岗岩体、石英闪长玢岩脉之间的联系,对花岗闪长岩、石英闪长玢岩进行了U--Pb年代学研究,并分别对花岗闪长岩、石英闪长玢岩、矿化蚀变岩和围岩的地球化学进行了系统测定。麻棚花岗岩体U--Pb年龄为(124.8±1.4)Ma(MSWD=0.74),石英闪长玢岩脉年龄为(127.3±1.1)Ma(MSWD=1.15),但二者地球化学特征表现不同,应有不同起源。地球化学特征表明,麻棚花岗岩与矿化蚀变岩具有较一致的稀土、微量元素配分型式,而与围岩差别大,说明金矿的成矿流体来源与麻棚花岗岩关系密切。此外,花岗闪长岩具高钾钙碱性,且重稀土亏损、轻稀土富集、弱Eu异常、高Sr--Ba和高Sr/Y、La/Yb比值,表明麻棚岩体的形成有幔源岩浆的混入。笔者认为成矿流体和成矿物质来源为幔源岩浆底侵和混合,并以花岗岩浆为载体而迁移上升。结合矿床地质特征,初次提出闪长玢岩脉与矿体时空关系密切,这应是闪长玢岩脉作为隔流体层对来自麻棚花岗岩体的成矿流体具有一定的封闭作用,使得矿化、蚀变富集产出,即岩脉封闭作用。石湖金矿的成岩成矿机制与中生代期间岩石圈减薄的地球动力学背景密切相关,应是一种非造山型金矿。     

Petrogenesis of Mafic to Felsic Plutonic Rock Associations: the Calc-alkaline Querigut Complex, French Pyrenees

The Quérigut mafic–felsic rock association comprisestwo main magma series. The first is felsic comprising a granodiorite–tonalite,a monzogranite and a biotite granite. The second is intermediateto ultramafic, forming small diorite and gabbro intrusions associatedwith hornblendites and olivine hornblendites. A U–Pb zirconage of 307 ± 2 Ma was obtained from the granodiorite–tonalites.Contact metamorphic minerals in the thermal aureole providea maximum emplacement pressure of between 260 and 270 MPa. Petrographiccharacteristics of the mafic and ultramafic rocks suggest crystallizationat <300 MPa, demonstrating that mantle-derived magmas ascendedto shallow levels in the Pyrenean crust during Variscan times.The ultramafic rocks are the most isotopically primitive components,with textural and geochemical features of cumulates from hydrousbasaltic magmas. None of the mafic to ultramafic rocks havedepleted mantle isotope signatures, indicating crustal contaminationor derivation from enriched mantle. Origins for the dioritesinclude accumulation from granodiorite–tonalite magma,derivatives from mafic magmas, or hybrids. The granitic rockswere formed from broadly Proterozoic meta-igneous crustal protoliths.The isotopic signatures, mineralogy and geochemistry of thegranodiorite–tonalites and monzogranites suggest crystallizationfrom different magmas with similar time-integrated Rb/Sr andSm/Nd isotope ratios, or that the granodiorite–tonalitesare cumulates from a granodioritic to monzogranitic parent.The biotite granite differs from the other felsic rocks, representinga separate magma batch. Ages for Quérigut and other Pyreneangranitoids show that post-collisional wrenching in this partof the Variscides was under way by 310 Ma. KEY WORDS: Variscan orogeny; Pyrenees; Quérigut complex; epizonal magmatism; post-thickening; mafic–felsic association     

Isotopic evidence for multiple contributions to felsic magma chambers: Gouldsboro Granite, Coastal Maine

The Gouldsboro Granite forms part of the Coastal Maine Magmatic Province, a region characterized by granitic plutons that are intimately linked temporally and petrogenetically with abundant co-existing mafic magmas. The pluton is complex and preserves a felsic magma chamber underlain by contemporaneous mafic magmas; the transition between the two now preserved as a zone of chilled mafic sheets and pillows in granite. Mafic components have highly variably isotopic compositions as a result of contamination either at depth or following injection into the magma chamber. Intermediate dikes with identical isotopic compositions to more mafic dikes suggest that closed system fractionation may be occurring in deeper level chambers prior to injection to shallower levels. The granitic portion of the pluton has the highest Nd isotopic composition (ε_Nd = + 3.0) of plutons in the region whereas the mafic lithologies have Nd isotopic compositions (ε_Nd = + 3.5) that are the lowest in the region and similar to the granite and suggestive of prolonged interactions and homogenization of the two components. Sr and Nd isotopic data for felsic enclaves are inconsistent with previously suggested models of diffusional exchange between the contemporaneous mafic magmas and the host granite to explain highly variable alkali contents. The felsic enclaves have relatively low Nd isotopic compositions (ε_Nd = + 2 – + 1) indicative of the involvement of a third, lower ε_Nd melt during granite petrogenesis, perhaps represented by pristine granitic dikes contemporaneous with the nearby Pleasant Bay Layered Intrusion. The dikes at Pleasant Bay and the felsic enclaves at Gouldsboro likely represent remnants of the silicic magmas that originally fed and replenished the overlying granitic magma chambers. The large isotopic (and chemical) contrasts between the enclaves and granitic dikes and granitic magmas may be in part a consequence of extended interactions between the granitic magmas and co-existing mafic magmas by mixing, mingling and diffusion. Alternatively, the granitic magmas may represent an additional crustal source. Using granitic rocks such as these with abundant evidence for interactions with mafic magmas complicate their use in constraining crustal sources and tectonic settings. Fine-grained dike rocks may provide more meaningful information, but must be used with caution as these may also have experienced compositional changes during mafic–felsic interactions.     

Coeval potassic and sodic calc-alkaline series in the post-collisional Hercynian Tanncherfi intrusive complex, northeastern Morocco: geochemical, isotopic and geochronological evidence

The post-collisional late Hercynian Tanncherfi intrusive complex (TIC) is part of a widespread intrusive episode in the Moroccan Meseta. The complex contains a wide range of rock types, from monzogabbros to monzogranites. Two distinct magmatic series are recognized: (1) a potassic (shoshonitic) series consisting of monzogabbros, quartz monzonites and monzogranites; and (2) a sodic (granodioritic) series represented by quartz monzodiorites and granodiorites. All the Tanncherfi plutonic rocks display similar spider-diagram profiles, with LILE and LREE enrichment and Nb, Ta, Ti depletion, which are typical of subduction-related magmas. Combined major, trace element compositions and Sr, Nd isotopic results indicate that the two series have been derived from a LILE- and LREE-enriched continental lithospheric mantle source, under different partial melting and/or depth conditions. Intrusion of the Tanncherfi rocks was not temporally related to subduction and the enrichment of their source is likely to be linked to preceding subduction events. The two series evolved by fractional crystallization, of clinopyroxene, plagioclase, hornblende, biotite, K-feldspar and accessories (Fe–Ti oxide minerals, titanite, apatite and zircon) for the potassic series while the sodic series combined fractional crystallization with assimilation of felsic magmas with lower Sr isotopic ratio than the more mafic term of the series, the quartz monzodiorite. The intrusion of the potassic magmas (344±6 Ma) marks a major change in the tectonic regime of eastern Meseta. These magmas intruded during post-thickening uplift and extension, both probably favored by convective thinning of the lithosphere. This model provides a reasonable mechanism for the genesis of other Hercynian intrusive complexes in Morocco.     

新疆阿尔泰南缘克因布拉克铜锌矿区黑云母二长花岗岩地球化学特征及意义

新疆阿尔泰南缘克因布拉克铜锌矿区出露大面积花岗岩,岩性主要为二长花岗岩、钾长花岗岩、黑云母花岗岩和英云闪长岩,矿体赋存于二长花岗岩与上志留统-下泥盆统康布铁堡组外接触带中。室内显微镜下鉴定二长花岗岩发育二云母二长花岗岩和黑云母二长花岗岩2种岩相。黑云母二长花岗岩具有高硅、高碱、贫钠富钾、准铝质-过铝质的特点;微量元素特征表现为Rb、Th、K、Ce、Nd、Tb富集,Ba、Nb、Sr、Ti强烈亏损;稀土元素配分模式为轻稀土相对富集的右倾型,具有稀土总量中等及中等负铕异常的特点。这些特征表明该花岗岩属于高钾钙碱性准铝质-过铝质S型。岩石的I_Sr(t)值为0.703 039~0.705 729,ε_Nd(t)值相对较低,多数为近于0的负值,T_2DM两阶段模式年龄集中在1.145~1.194 Ga。岩石可能由中元古界富含黑云母的变质砂岩或正变质岩和少量幔源物质在较低压力条件下熔融形成,源区有斜长石的残留。地球化学特征表明该区花岗岩具有良好的含矿性,其矿床形成于后碰撞的伸展环境,成矿作用与二长花岗岩的岩浆期后热液有关。     

He–Ar and Nd–Sr isotopic compositions of late Pleistocene felsic plutonic back arc basin rocks from Ulleungdo volcanic island, South Korea: Implications for the genesis of young plutonic rocks in a back arc basin

We report analyses of noble gases and Nd–Sr isotopes in mineral separates and whole rocks of late Pleistocene (< 0.2 Ma) monzonites from Ulleungdo, South Korea, a volcanic island within the back arc basin of the Japan island arc. A Rb–Sr mineral isochron age for the monzonites is 0.12 ± 0.01 Ma. K–Ar biotite ages from the same samples gave relatively concordant ages of 0.19 ± 0.01and 0.22 ± 0.01 Ma. ⁴⁰Ar/³⁹Ar yields a similar age of 0.29 ± 0.09 Ma. Geochemical characteristics of the felsic plutonic rocks, which are silica oversaturated alkali felsic rocks (av., 12.5 wt% in K₂O + Na₂O), are similar to those of 30 alkali volcanics from Ulleungdo in terms of concentrations of major, trace and REE elements. The initial Nd–Sr isotopic ratios of the monzonites (⁸⁷Sr/⁸⁶Sr = 0.70454–0.71264, ¹⁴³Nd/¹⁴⁴Nd = 0.512528–0.512577) are comparable with those of the alkali volcanics (⁸⁷Sr/⁸⁶Sr = 0.70466–0.70892, ¹⁴³Nd/¹⁴⁴Nd = 0.512521–0.512615) erupted in Stage 3 of Ulleungdo volcanism (0.24–0.47 Ma). The high initial ⁸⁷Sr/⁸⁶Sr values of the monzonites imply that seawater and crustally contaminated pre-existing trachytes may have been melted or assimilated during differentiation of the alkali basaltic magma.A mantle helium component (³He/⁴He ratio of up to 6.5 RA) associated with excess argon was found in the monzonites. Feldspar and biotite have preferentially lost helium during slow cooling at depth and/or during their transportation to the surface in a hot host magma. The source magma noble gas isotopic features are well preserved in fluid inclusions in hornblende, and indicate that the magma may be directly derived from subcontinental lithospheric mantle metasomatized by an ancient subduction process, or may have formed as a mixture of MORB-like mantle and crustal components. The radiometric ages, geochemical and Nd–Sr isotopic signatures of the Ulleungdo monzonites as well as the presence of mantle-derived helium and argon, suggests that these felsic plutonic rocks evolved from alkali basaltic magma that formed by partial melting of subcontinental lithospheric mantle beneath the back arc basin located along the active continental margin of the southeastern part of the Eurasian plate.     

Geochemistry and petrogenesis of an adakitic quartz-monzonitic porphyry stock and related cross-cutting dike suites,Kighal, northwest Iran

A late Oligocene–early Miocene quartz-monzonitic porphyry stock intrudes upper Eocene andesitic-latitic lava flows, producing Cu–Mo mineralization and hydrothermal alteration zones in the Kighal area, northwest Iran. Numerous cross-cutting dikes of various compositions, ranging from quartz-diorite to granodiorite and microdiorite, branch off from three later-stage barren sub-volcanic bodies, and intrude the porphyry stock. Both the stock and comagmatic dikes display I-type, magnesian, calc-alkaline to high-K calc-alkaline signatures and metaluminous to peraluminous geochemical characters, being emplaced within an active continental margin setting. Analysed samples display the typical geochemical characteristics of adakites. Moreover, rare earth elements exhibit a fractionated pattern with low heavy rare earth element concentrations. The general trend in an La/Yb–Yb diagram shows that partial melting, rather than fractional crystallization, was the dominant process of magma generation. Based on the compositional classification of modern adakites, the studied rocks are of high-SiO₂ adakite type. They were generated through low degrees of high-pressure partial melting of subducted rutile- and amphibole-bearing eclogitic Neo-Tethyan oceanic slab. The descending slab underwent break-off, leaving behind a residue rich in garnet + amphibole ± rutile, lacking significant plagioclase. Interaction of the slab-derived magma with the mantle-wedge peridotite is also evident.     

西秦岭三叠纪酸性侵入岩中高An值斜长石的成因及其地质意义

研究I型花岗岩中再循环晶的成分和结构特征，对揭示岩浆系统的形成和演化历史以及壳源和幔源岩浆的相互作用具有重要的意义。本文以西秦岭北西段三叠纪过马营复式岩体内的不同造岩矿物为主要研究对象，通过对具有不同结构特征的斜长石"粗晶"和黑云母展开电子探针（EMPA）、LA-ICP-MS微量元素面扫描、原位Sr同位素分析，来探讨含高An斜长石的成因，示踪不同岩浆房端员的属性，约束岩浆演化过程并建立多级岩浆房模型。过马营复式岩体的岩性分为偏铝质花岗岩类和过铝质花岗闪长岩类，两类岩性中均存在An值呈突变的筛状结构斜长石，即高An（72~85）区与低An（20~55）区在同一颗粒中并存，其对应主、微量元素也存在截然变化。与低An区相比，高An区具有高Fe、Mg，高Ba的特征。高钙区斜长石可进一步分为两类，第1类高钙区斜长石（An₈₀-₈₅），和第2类高钙区斜长石（An₇₂-₇₈）。第1类高钙区比第2类高钙斜长石区具有更高的Ca、Al、Fe、Mg、Ba含量。本研究中斜长石晶体存在核_高An-边_低An与核_低An-幔_高An-边_低An两种不同类型的环带结构，表明其各自的生长过程有所不同。高An区与低An区之间An值跳跃式的变化与对应主、微量元素Fe、Mg、Sr、Ba含量特征均指示斜长石成分差异并非晶内扩散、动力学作用以及物理条件的变化造成的，更可能形成于开放的岩浆系统。本文认为斜长石粗晶为再循环晶，其内部的高An区形成于深部富H₂O玄武质岩浆，低An区形成于浅部酸性岩浆房（偏铝质与过铝质）。两种不同高钙区斜长石及其对应的主、微量元素差异指示它们很可能结晶于两批次不同的玄武质岩浆，其中第1类高钙区斜长石的母岩浆相对更富Fe、Mg、Ba。两种玄武质岩浆携带高An斜长石沿岩浆通道向上运移，上升过程熔蚀先前结晶的高An斜长石，将其带入浅部酸性岩浆房后与内部花岗质/花岗闪长质岩浆发生混合。混合之后的岩浆沿高An斜长石残晶边部继续结晶生长，同时高温玄武质岩浆的注入导致浅部岩浆房已结晶的低An斜长石被熔蚀形成筛状结构，随后玄武质岩浆、混合后岩浆依次沿其边部继续生长。我们认为两批次的玄武质岩浆体积较小并未对浅部酸性岩浆房成分造成大的影响。     

The Origin and Features of the Two Intermediate-Acid Intrusive Series in Tongling Area, Anhui, China

1. Introduction Tongling district is situated in the southern part of the Yangtze River, Anhui province, China (Fig. 1). It is one of the most important metal basements in China, being rich copper material resources, also named "ancient copper capital of China". Studies showed that each copper ore deposit is bound up with the intermediate-acid intrusive rocks in the area. Therefore, many researchers (e.g. Chang Yinfu et al, 1987; Xing Fengming, et al, 1995; Zhou Xinrou, et al, 1993; and…     

Interaction between mafic and felsic magmas in subvolcanic environment (Tastau igneous complex,eastern Kazakhstan)

The paper reports the results of integrated geological, petrological, geochemical, and geochronological studies of the Tastau igneous ring complex in the Zaisan orogen of eastern Kazakhstan. Interaction between felsic and mafic magmas has been studied. Hybrid rocks are represented by gabbros and diorites injected into a granitic magma chamber. They occur as dikes and pillow-like and globular mafic bodies variously disintegrated and mixed with host granitoids. The age of synplutonic rocks is 242 ± 20 Ma (U/Pb zircon dating), which is, with regard to analytical error, substantially younger than it was presumed.Mechanisms of interaction between felsic and mafic magmas have been studied. They include mechanical (mingling) and chemical (mixing) interaction, which produce composite mixtures and hybrid rocks. The ratios of mafic to felsic components involved in the formation of intermediate rocks were calculated from major elements by regression analysis and tested with regard to rare and trace elements. The model for mingling includes rapid quenching of the mafic melt when it is injected into the granitic magma chamber, decomposition of crystalline fragments, dispersion of fragments and crystals in the magma chamber under conditions of rapid turbulent flow, and enrichment of felsic magma with femic components to produce monzonitic magmas.     

Evidence for hybridisation in the Tynong Province granitoids,Lachlan Fold Belt,eastern Australia

The role of mafic–felsic magma mixing in the formation of granites is controversial. Field evidence in many granite plutons undoubtedly implies interaction of mafic (basaltic–intermediate) magma with (usually) much more abundant granitic magma, but the extent of such mixing and its effect on overall chemical features of the host intrusion are unclear. Late Devonian I-type granitoids of the Tynong Province in the western Lachlan Fold Belt, southeast Australia, show typical evidence for magma mingling and mixing, such as small dioritic stocks, hybrid zones with local host granite and ubiquitous microgranitoid enclaves. The latter commonly have irregular boundaries and show textural features characteristic of hybridisation, e.g. xenocrysts of granitic quartz and K-feldspars, rapakivi and antirapakivi textures, quartz and feldspar ocelli, and acicular apatite. Linear (well defined to diffuse) compositional trends for granites, hybrid zones and enclaves have been attributed to magma mixing but could also be explained by other mechanisms. Magmatic zircons of the Tynong and Toorongo granodiorites yield U–Pb zircon ages consistent with the known ca 370 Ma age of the province and preserve relatively unevolved ?_Hf (averages for three samples are +6.9, +4.3 and +3.9). The range in zircon ?_Hf in two of the three analysed samples (8.8 and 10.1 ?_Hf units) exceeds that expected from a single homogeneous population (～4 units) and suggests considerable Hf isotopic heterogeneity in the melt from which the zircon formed, consistent with syn-intrusion magma mixing. Correlated whole-rock Sr–Nd isotope data for the Tynong Province granitoids show a considerable range (0.7049–0.7074, ?_Nd +1.2 to –4.7), which may map the hybridisation between a mafic magma and possibly multiple crustal magmas. Major-element variations for host granite, hybrid zones and enclaves in the large Tynong granodiorite show correlations with major-element compositions of the type expected from mixing of contrasting mafic and felsic magmas. However, chemical–isotopic correlations are poorly developed for the province as a whole, especially for ⁸⁷Sr/⁸⁶Sr. In a magma mixing model, such complexities could be explained in terms of a dynamic mixing/mingling environment, with multiple mixing events and subsequent interactions between hybrids and superimposed fractional crystallisation. The results indicate that features plausibly attributed to mafic–felsic magma mixing exist at all scales within this granite province and suggest a major role for magma mixing/mingling in the formation of I-type granites.     

Genesis and Mixing/Mingling of Mafic and Felsic Magmas of Back-Arc Granite: Miocene Tsushima Pluton, Southwest Japan

The Middle Miocene Tsushima granite pluton is composed of leucocratic granites, gray granites and numerous mafic microgranular enclaves (MME). The granites have a metaluminous to slightly peraluminous composition and belong to the calc‐alkaline series, as do many other coeval granites of southwestern Japan, all of which formed in relation to the opening of the Sea of Japan. The Tsushima granites are unique in that they occur in the back‐arc area of the innermost Inner Zone of Southwest Japan, contain numerous miarolitic cavities, and show shallow crystallization (2–6 km deep), based on hornblende geobarometry. The leucocratic granite has higher initial ⁸⁷Sr/⁸⁶Sr ratios (0.7065–0.7085) and lower ε_Nd(t) (?7.70 to ?4.35) than the MME of basaltic–dacitic composition (0.7044–0.7061 and ?0.53 to ?5.24), whereas most gray granites have intermediate chemical and Sr–Nd isotopic compositions (0.7061–0.7072 and ?3.75 to ?6.17). Field, petrological, and geochemical data demonstrate that the Tsushima granites formed by the mingling and mixing of mafic and felsic magmas. The Sr–Nd–Pb isotope data strongly suggest that the mafic magma was derived from two mantle components with depleted mantle material and enriched mantle I (EMI) compositions, whereas the felsic magma formed by mixing of upper mantle magma of EMI composition with metabasic rocks in the overlying lower crust. Element data points deviating from the simple mixing line of the two magmas may indicate fractional crystallization of the felsic magma or chemical modification by hydrothermal fluid. The miarolitic cavities and enrichment of alkali elements in the MME suggest rapid cooling of the mingled magma accompanied by elemental transport by hydrothermal fluid. The inferred genesis of this magma–fluid system is as follows: (i) the mafic and felsic magmas were generated in the mantle and lower crust, respectively, by a large heat supply and pressure decrease under back‐arc conditions induced by mantle upwelling and crustal thinning; (ii) they mingled and crystallized rapidly at shallow depths in the upper crust without interaction during the ascent of the magmas from the middle to the upper crust, which (iii) led to fluid generation in the shallow crust. The upper mantle in southwest Japan thus has an EMI‐like composition, which plays an important role in the genesis of igneous rocks there.     

Geology and petrology of the archean high-K and high-Mg Panozero massif,Central Karelia

The high-K and high-Mg Panozero central-type intrusion is located on the shore of Lake Segozero, Central Karelia, and has an age of 2737 ± 10 Ma. Detailed mapping and petrological study showed that it was formed in three magmatic cycles that were separated by lamprophyre dikes. The first cycle is composed mainly of mafic rocks (layered complex: pyroxenites-honblendites-monzogabbro) and monzonites 1; the second cycle includes monzonites 2, and the third cycle comprises monzonites 3 and quartz monzonites. The massif is cut by numerous lamprophyre dikes and breccia zones. As compared to calc-alkaline series, the studied rocks are enriched in K, Ba, Sr, P, LREE, have high mg# (mg# = 0.5–0.65), and elevated contents of Cr and Ni. The parent composition of the layered complex was determined to be monzogabbro. Model calculations showed that the compositional variations of the Panozero Complex are consistent with the fractional crystallization of monzogabbro. The melts were fractionated in an intermediate chamber and during the flowing and crystallization of the magma. The parent melt of the intrusion was formed by the partial melting of mantle enriched in some LILE, LREE, and volatiles (CO₂ and H₂O). The volatile enrichment of the melt manifests itself in the mineral composition of the rocks, the presence of primary gas inclusions in apatite, and diverse structural features. The comparison of the rocks of the Panozero Massif with metasomatized mantle xenoliths in the variation diagrams for incompatible elements showed that the mantle source of the Panozero Complex was metasomatized by fluid consisting of H₂O and CO₂ of different origin.